On a route that is defined by rural roads or secondary roads, a greater number of navigating instructions and, if applicable, also more complex navigating instructions are required than on a route that is predominantly characterized by an expressway or a straight section due to the more complex routing. However, a route also may alternately consist of complex and less complex sections, for example, when the driver exits the expressway in order to drive into a large city. As the road network becomes denser, one encounters the problem that a few of the navigating instructions do not correctly fit the concrete situation such that the driver of the vehicle becomes confused because he is unable to relate the navigating instructions of the navigation device to the actual route lying ahead.
Various approaches for solving this problem are known. For example, the scale of the illustration shown on the display of the navigation device is changed in accordance with fixed criteria due to the manual intervention of the driver on the navigation device, namely such that the route sections lying ahead are enlarged. The relevant map section for the driver needs to be chosen, for example, by means of a manual graphic selection in such instances and then manually altered with respect to the attention to detail with a zoom function. This distracts the driver from the traffic.
It is also known to zoom in on approaching turning maneuvers. This principle is disclosed in the U.S. Pat. No. 6,529,822 B1. In said patent, the complexity of route sections is determined by means of the starting points and end points of straight route sections, as well as by means of so-called “shape points” that are arranged within and along non-straight route sections. Depending on the route complexity defined by means of these points, route sections are illustrated on a different scale on the display of the navigation device. On complex route sections, the scale is steadily changed until a limiting value is reached depending on the degree to which the route section fills out a predefined frame or the available display, respectively. The change back to the so-called overview mode does not take place until the vehicle has passed the complex route section and a less complex route section should once again lie ahead.
The disadvantage of this solution can be seen in that the driver can lose the orientation with respect to the route lying ahead while maneuvering through the complex route section due to the lack of a corresponding overview. Signposts provided at the current location or other roadside information cannot be effectively utilized for independently carrying out turns at short notice or for noticing available alternative routes in a timely fashion. The utmost concentration of the driver is required, in particular, on complex route sections such that the driver should not perform any complicated inputs on the navigation device while navigating through these route sections because this also distracts the driver from the traffic.